A head actuator supports a head slider and designed to swing around a support shaft over first and second swinging ranges adjacent each other. A restraint member is designed to restrain the swinging movement of the head actuator from separating from the first swinging range toward the second swinging range. A restriction member is designed to restrict the swinging movement of the head actuator from separating from the second swinging range toward the first swinging range. The second swinging range is excluded from the actual swinging range of the head actuator when the restraint member operates. The swinging range of the head actuator can thus be reduced or narrowed. Likewise, the first swinging range is excluded from the actual swinging range of the head actuator when the restriction member operates. The swinging range of the head actuator can thus be reduced or narrowed.